Normal bacteria called intestinal bacteria are present in the intestine, and a distributed state of these bacteria is referred to as an intestinal bacterial flora. A Salmonella relative to colibacillus belonging to Enterobacteriaceae etc., a Bacteroides, a Eubacterium, a Bifidobacterium, a Peptostreptococcus, a Clostridium, a Lactobacillus and the like are included in the intestinal bacteria.
While these intestinal bacteria perform ancillary parts for digestion of food and contribute to maintenance of physical condition by suppressing growth of alien pathogenic fungi etc., such an intestinal bacterial flora is not constant in each individual but varies with the age, food habituation etc. of the host. It is known that the intestinal bacteria flora varies with a disease, mental stress or the like in the same individual.
When analyzing such an intestinal bacterial flora, cultivation has been utilized in general. That is, each intestinal bacterium has been identified on the basis of the characters of the bacterium by planting a sample such as dejection of the subject in a selective medium or a non-selective medium or the like, cultivating each medium in accordance with growth conditions for each bacterium and dyeing the growing bacterium or the like.
However, it is said that intestinal bacterial groups amount to 100 types (“Intestinal Flora and Probiotics” (INTESTINAL FLORA AND PROBIOTICS)”, Proceedings of V. Symposium of Intestinal Flora, Tokyo, 1996, Japan Scientific Societies Press), it is extremely difficult to analyze these numerous intestinal bacterial groups by cultivation, and it follows that the range of analyzable bacteria is also limited. Even if analysis is possible as to a constant range of bacterial groups, it has been work requiring time and labor for cultivating and identifying a large number of bacteria.
Also in the bacterium, on the other hand, genetic information where the qualities of the respective bacteria are recorded is coded in chromosomes as DNA. The difference between the qualities of these bacteria is reflected on the sequence of chromosomes controlling this genetic information, and characteristic sequence is present every bacterium.
For example, it is shown that 16S rDNA coding 16S rRNA subunits of ribosomal RNA of bacteria varies between the bacteria and the bacteria can be identified by this difference in sequence (Christine et al., Appl. Environ. Microbiol. 65: 102-109).